1. Field of the Invention
Aspects of the present invention relate to a developing unit and an electrophotographic image forming apparatus with the same. More particularly, aspects of the present invention relate to a developing unit having a simple structure for driving internal rotary components and an electrophotographic image forming apparatus with the same.
2. Description of the Related Art
Typically, an electrophotographic image forming apparatus, such as a laser printer or a digital copier, radiates a light beam across a photoconductor charged to a predetermined potential to form an electrostatic latent image on the photoconductor, applies toner (a developing agent) to the electrostatic latent image to develop the electrostatic latent image into a visible toner image, transfers the visible toner image to a print medium, and fuses the toner image onto the print medium to print a predetermined image. Such an electrophotographic image forming apparatus includes a developing unit to contain the toner and to develop the electrostatic latent image into a visible toner image by applying the toner to the photoconductor.
FIGS. 1 and 2 are plan views illustrating arrangements of gears for driving rotary components of conventional developers.
Referring to FIG. 1, a developing unit 10, which is an example of a conventional developer, includes a photoconductor gear 11 to drive a photoconductor (not shown), a first idle gear 15 engaged with the photoconductor gear 11, a second idle gear 16 engaged with the first idle gear 15, and a third idle gear 17 engaged with the second idle gear 16. The second idle gear 16 is also engaged with a developer roller gear 12 and a toner-supply roller gear 13. The developer roller gear 12 drives a developer roller (not shown), and the toner-supply roller gear 13 drives a toner-supply roller (not shown). The third idle gear 17 is also engaged with an agitator gear 14 to drive an agitator (not shown).
The photoconductor gear 11 is coupled to an external driving unit (not shown). The external driving unit drives the photoconductor gear 11 clockwise when a printing operation starts. Upon the rotation of the photoconductor gear 11, the idle gears 15, 16, and 17 are rotated. As a result, the developer roller gear 12 and the toner-supply roller gear 13, which are engaged with the second idle gear 16, are rotated counterclockwise, and the agitator gear 14 engaged with the third idle gear 17 is rotated clockwise.
Referring to FIG. 2, a developing unit 20, which is another example of a conventional developer, includes a photoconductor gear 21 coupled to an external driving unit (not shown), a developer roller gear 22 engaged with the photoconductor gear 21, a first idle gear 25 engaged with the developer roller gear 22, and a second idle gear 26 engaged with the first idle gear 25. The first idle gear 25 is also engaged with a toner-supply roller gear 23, and the second idle gear 26 is also engaged with an agitator gear 24.
When an electrophotographic image forming apparatus performs a printing operation, the external driving unit rotates the photoconductor gear 21 clockwise. As a result, the developer roller gear 22 is rotated counterclockwise, the first idle gear 25 is rotated clockwise, and the second idle gear 26 is rotated counterclockwise. The toner-supply roller gear 23 engaged with the first idle gear 25 is rotated counterclockwise, and the agitator gear 24 engaged with the second idle gear 26 is rotated clockwise.
As shown in FIGS. 1 and 2, the developing units 10 and 20 require at least two idle gears as well as gears provided at one side of each of the rotary components to drive each rotary component, such as a photoconductor, a developer roller, a toner-supply roller, and an agitator, thereby increasing the possibility of malfunctions in the developing unit, and the complexity, size, and manufacturing cost of the developing unit. Further, this complicated gear system causes a photoconductor to be rotated at non-uniform speed or periodically vibrated during rotation. Abnormal horizontal lines, known as jitter, may be present in a printed image because of this non-uniform rotation and periodic vibration of the photoconductor.